Replace pure EE subscription area items

specific items that are in ee and are clear are subscription related should use gitlab_subscriptions instead.

Plan

• part one - Replace use of should_check_namespace_plan? fro... (!193941 - merged)
• part two - Replace use of should_check_namespace_plan? fro... (!206223 - merged)
• part three Replace use of should_check_namespace_plan? part 4 (!206768 - merged)
• part four Replace final app directory use of should_check... (!207167 - merged)
• part five Replace lib directory use of should_check_names... (!207297 - merged)